1. Technical Field
The invention relates to a flange bearing half shell having a bearing shell and two thrust washers arranged on said bearing shell.
2. Related Art
The invention also relates to a flange bearing having two flange bearing half shells, each of which comprises a bearing shell, at least one bearing shell having two thrust washers arranged on said bearing shell.
The invention also relates to a thrust washer for a flange bearing half shell, which takes the form of a ring segment.
Such flange bearings are used for example in internal combustion engines for bearing-assisted mounting of the crankshaft in the crankcase. Due to the right-angle bends in the crankshaft, the flange bearings are in principle constructed in two parts, in the form of two flange bearing half shells, with a view to facilitating mounting. Crankshafts of dismantlable modular construction are also to be found, which allow the use of one-part flange bearings, but these are still very much the exception in mass production, in particular due to the high manufacturing costs.
The bearing shell serves to absorb radial bearing forces, which are introduced via the shaft rotating in the bearing shell, whereas the thrust washer, of which there is at least one, serves to absorb axial forces. If there is a need to absorb axial forces in both directions of the shaft, two thrust washers have to be provided, since each thrust washer is only in a position to absorb the forces directed towards its overlay.
Cheeks are provided on the shaft, by means of which the shaft is supported on the thrust washer.
As a rule, the crankshaft bearing arrangement comprises a plurality of radial plain bearings, i.e. a plurality of bearings without thrust washers, and one combined radial/axial plain bearing. This radial/axial plain bearing has the thrust washers necessary for absorbing axial forces. Reference is made below to the combined radial/axial plain bearing, since it is this plain bearing construction which substantially constitutes the subject matter of the invention.
The flange bearings conventionally constructed in two parts in the form of two flange bearing half shells are preliminarily mounted in such a way in the crankcase that, prior to insertion of the crankshaft, the upper flange bearing half shell is positioned in the upper half of the crankcase and the lower flange bearing half shell is positioned in the lower half, or “cover”, of the crankcase.
The upper half of the crankcase is the part of the crankcase which is connected with the engine block, i.e. the part of the crankcase which is arranged between the crankshaft and the cylinder head. The upper case half is, as indeed is the entire crankcase, essentially a casting, which is post-machined and comprises a bearing saddle for accommodating the upper flange bearing half shell, onto which the upper flange bearing half shell is fitted during mounting.
As a rule, the upper flange bearing half shell has a hole, through which the plain bearing is supplied with oil. The oil itself is fed as far as into the bearing saddles of the crankcase by means of feed lines. Consequently, care must be taken when fitting the upper flange bearing half shell to ensure that the oil supply hole in the bearing shell is aligned with the outlet of the oil supply line in the bearing saddle. A central and thus symmetrical arrangement of the hole is not expedient, since the supply hole has as a rule to be arranged eccentrically due to pressure distribution in the plain bearing lubricating oil film. Incorrect positioning of the upper flange bearing half shell in the bearing saddle and thus closure of the oil supply line results in inadequate oil supply to the plain bearing and, in the worst case scenario, to dry running of the bearing and bearing destruction.
For this reason, mounting aids are provided to assist in mounting. It is usual in practice to arrange a lug-type, outwardly projecting cam on the outer circumferential surface of the bearing shell, wherein a recess corresponding to said cam is provided in the bearing saddle of the crankcase. The flange bearing half shell, with its outwardly projecting cam, can then only be properly mounted in the bearing block when cam and recess fit together, i.e. the oil supply hole of the bearing shell is aligned with the outlet opening of the oil supply line in the bearing saddle and the flange bearing half shell is correctly oriented.
Constructing the mounting aid as a cam and corresponding recess is complex, due to the manufacturing process which has to be carried out, and requires a plurality of operations. The outwardly projecting cam is generated by a stamping process. The plain bearing material which is detached from the bearing shell in the process has to be carefully removed, so that loose particles do not become the cause of bearing fretting after mounting and during operation of the internal combustion engine.
Apart from the absent oil supply hole, the lower flange bearing half shell is of the same construction as the upper flange bearing half shell. It too has a cam as mounting aid.
The lower half shell of the flange bearing is arranged in the crankcase cover. To this end, the bearing cover is provided in the case cover to accommodate the lower flange bearing half shell. Together with the bearing saddle arranged in the upper case part, the bearing cover forms the receptacle for the flanged bearing, wherein the bearing saddle accommodates the upper flanged bearing half shell and the bearing cover the lower flanged bearing half shell.
After preliminary mounting, i.e. fitting the two flange bearing half shells into the upper case part and the case cover respectively and carrying out the remaining preliminary operations, the upper case part is fitted together with the case cover and screwed thereto, so as thus to form a closed crankcase.
The two crankcase parts do not as a rule have any centering devices which fixedly determine the relative position of these two components to one another. The screw connections provided in the crankcase, which connect the case cover firmly to the upper case part, by their nature exhibit a clearance and cannot for this reason serve as centering devices, such that the case cover may be moved, in particular by up to a few tenths of a millimeter in the direction of the crankshaft axis, relative to the upper case part once the screws have been screwed in but not tightened.
The two-part crankcase consisting of the upper case part and the case cover is generally divided along a straight line, i.e. the bearing cover and the bearing saddle, which together form the receptacle for the flange bearing, each have a semicircular recess extending over an angle of 180°, into which the flange baring half shells may be inserted. These flange bearing half shells are likewise generally divided along a straight line and extend over an angle of 180°.
If, as already explained, the case cover is displaceable and uncentered relative to the upper case part in the direction of the crankshaft axis due to the lack of a centering device, the lower flange bearing half shell may also be displaced relative to the upper flange bearing half shell. Neither of the two flange bearing half shells is purposefully oriented and fixed with regard to the flange baring half shell opposite it.
If the two flange bearing half shells are axially offset, the two thrust washers arranged to the left of the bearing bore or to the right of the bearing bore do not lie in a plane, such that on the one hand the bearing absorbs forces or fulfills its task of providing axial guidance and support for the crankshaft only on the thrust washer which protrudes further axially. On the other hand, overloading of the only partially stressed bearing may occur.
Against this background, it is the object of the present invention to provide a measure which ensures that the two flange bearing half shells of a flange bearing are aligned with one another when fitted and to provide a device with which the crankcase cover is centered in the upper part of the crankcase.